The present invention relates generally to a hermetic compressor and, more particularly, to a compressor having a reciprocating piston compressing fluid for flow past a discharge valve assembly.
A hermetic compressor comprises a hermetically sealed housing having a compressor mechanism mounted therein. The compressor mechanism may include a crankcase or cylinder block defining a compression chamber in which gaseous refrigerant is compressed and subsequently discharged.
A disadvantage to prior compressor designs is that there is always a certain volume left in the cylinder when the piston is at top dead center position. This volume of gas never leaves the cylinder but is repetitively compressed and re-expanded during the reciprocation of the piston. Re-expansion volume causes a loss of energy efficiency in a compressor.
In prior art compressors utilizing discharge valve designs disclosed, for example, in U.S. Pat. Nos. 2,117,601 and 4,834,632, the discharge valve member is mounted adjacent to and is seated against a valve plate and is axially displaceable in a space above the valve plate limited in movement by the valve plate top surface and a valve retainer.
It has long been recognized that valve design plays a crucial role in reliable and efficient operation of compressors. The reliability depends upon the dynamic behavior of the valve and the properties of the material from which the valve is made. Use of steel in ring or reed type valves is common in prior art compressors. The ability of some valve steels to resist the stress created by repeated bending and impacts caused by collision of a valve member with its seat is one of the essential properties of prior art valve materials. A valve material with higher damping characteristics would absorb induced stress peaks more efficiently, minimize valve damage and reduce noise generated by such impacts.
Prior steel valve members deformed by aerodynamic forces will form valve member to valve seat gaps, the dimensions and shape of which vary. Most prior compressors have a valve plate including surfaces at right angles to the outer face of the plate. Such valving system designs have a clearance volume at the sharp edges of the discharge port of the valve plate creating a turbulent flow and vortices due to the separation of the flow boundary layer at the valve seat outlet. This phenomenon affects the pressure distribution upon the valve surface, while increasing pressure losses and consequently reducing the performance of the compressor.
An objective of the proposed invention is to provide a reliable discharge valve system with an improved design for gas passage to increase valve flow area and minimize the pressure drop and cylinder reexpansion volume. The present invention also reduces turbulence formation, decreases noise generated by the valving system and is inexpensive to manufacture.